Electronic rider roll control system

ABSTRACT

An electronic rider roll control system for controlling the nip forces between a paper-winding roll and the winder drums solves for the actual nip by electrical analog as a function of winding roll diameter, the geometry of the winding roll and winder drums, the density, of the paper, the width of the roll being wound, and the relieving pressure applied by the rider roll counterbalancing system. The actual nip is compared with the desired nip as determined by a nip set point controller and is controlled accordingly. The starting nip and nip slope may also be simply controlled.

United States Patent I 72] Inventor John David Pfeliier Downingtown, Pa.

2 I 1 Appl, No. 885,504

I 22 1 Filed Dec. 16, 1969 I45! Patented Aug. I7, l97l 73] Assignec llclolt Corporation Beloit, Wis.

[54] ELECTRONIC RIDER ROLL CONTROL SYSTEM 26 Claims, 3 Drawing Figs.

[52] US. Cl 242/66 [51] Int. Cl. B65h 17/08 [50] Field 0! Search 242/55, 56, 56.2, 56.9, 57, 65, 66, 67.1, 67.5, 75.5, 75.51, V 75.53

[56] References Cited UNITED STATES PATENTS 2,165,111 7/1939 Rasmussen 242/66 Irimary Examiner-Stanley N. Gilreath Assistant Examiner-Werner H. Schroeder Atlorney- Larson, Taylor & Hinds ABSTRACT: An electronic rider roll control system for controlling the nip forces between a paper-winding roll and the winder drums solves for the actual trip by electrical analog as a function of winding roll diameter, the geometry of the winding roll and winder drums, the density, of the paper, the width of the roll being wound, and the relieving pressure applied by the rider roll counterbalancing system. The actual nip is compared with the desired nip as determined by a nip set point controller and is controlled accordingly. The starting nip and nip slope may also be simply controlled.

SUPPLY PRESSURE PRESSURE OPERATED POT PATENTEDAUBHIQH 9.599.889

SERVO N lBO I82 WK SUPFLY PRESSURE m. v 5 9 leeyvvm PRESSURE OPERATED POT I I FIG 1 mvmmn JOHN D. PFEIFFER ELECTRONIC RIDER ROLL CONTROL SYSTEM FIELD OF THE INVENTION The present invention relates to rider roll control system for controlling the nip forces applied against the winder drums of a winding assembly for paper rolls and the like.

" BACKGROUND OF THE INVENTION A typical two-drum-winding assembly includes a pair of spaced winder drums and a core shaft which when winding is begun is cradled between the drums and which moves vertically relative to the drums as the roll is built up thereon. In order to wind the paper on the core shaft and to prevent jerky movement of the roll and the loss of nip force (nip forces being the normal forces applied to the drums) a rider roll mounted above the .paper roll and bearing thereagainst is used. As the diameter of the paper roll increases a point is reached where the weight of the paper roll is sufficient to provide the necessary nip forces and the rider roll can be retracted, i.e., lifted off of the wound roll. When lift off takes place at the improper time a sudden change in the amount of tension produced in the winding roll occurs which may cause a number of problems including registration errors and offsetting of the web. Further, the application of too much rider roll pressure as the winding roll reaches large diameters may cause the tension to be so high as to cause bursting of the web or breaking of the web across the machine with consequent hidden damage wound into the roll or even failure of the entire winding process. Thus the need for reliable rider roll control is easily appreciated.

A number of systems have been devised for rider roll control, perhaps the most common utilizing a control cam or cams for controlling the operation of an air pressure regulator in accordance with the profile thereof. However, a number of variables such as the diameter of the winding roll, the geometry of the roll and winder drum assembly, the density of the material being wound on the winding drum, the width of the roll, and the relieving pressure exerted by the counterbalancing system will affect the rider roll pressure required and thus a change in any of these variables will necessitate the design and use of a different .cam. Thus, theoretically, a very large number of cams must be provided to ensure proper rider roll control when there is a change in one of the variables listed above and this is of course a serious disadvantage. Further, in practice, for example where thev grade of paper being wound is changed at a mill a different width of paper is being wound on the winding roll rather than changing cams assuming such cams were available, the operator is more likely to merely use the same cam which maywell provide entirely inappropriate control of the rider roll pressure and may lead to the various problems discussed above.

SUMMARY OF THE INVENTION 'In accordance with the invention, an electronic rider roll control system is provided which is adapted to take into account changes in the various factors discussed hereinabove without the need for changing cams or the like. Among a number of important features thereof, the system permits programming ofthe nip as the roll builds in size and permits direct dialing into the system of the density of paper in pounds by the operator. The desired nip force may also be directly selected by the operator, the selection controls being calibrated in units which are. meaningful to him. In addition, the actual nip force on the. winder drums is also conveniently expressed in meaningful-units.

Another very important feature of the invention is that a direct reading of theinip. force is. expressed in terms of force per unit width. is provided electrically without necessitating the use of loadrcells andwithout the need to go underneath the winder drums withsuch cells to provide nip measurements.

The system utilizes high gain integrated circuit operational amplifiers which themselves provide a number of advantages particularly in the areas of reliability and system stability.

In addition, a number of different readouts regarding various system parameters are provided which are useful as supervisory information as well as inputs for other systems. V

In general, the system utilizes a pulley arrangement for scaling down certain of the geometrical relationships between winding roll and winder drums, thisinformation being converted into proportional electrical signals by potentiometers responsive to the movement of the pulleys. These signals are used to produce a signal corresponding' to the actual weight of the paper roll which is, of course, varying as the roll is being built up. This signal is added to a signal corresponding to the total steel load provided by the rider roll to produce a signal proportional to the total vertically downwardly acting forces exerted on the winder drums. The rider roll load signal is produced by algebraically summing a fixed signal proportional to the dead weight of the rider roll with a signal corresponding to the counterbalancing force produced by the counterbalancing system and determined by a pressure-sensing potentiometer. The total force signal is resolved into the vector components thereof which act normally to the points of contact of the winding roll with the winder drums. An operational amplifier connected as a summing amplifier is used to multiply the total force signal by the cosine of the angle between the vertical and a line from the axis of the winding roll to the contact point mentioned hereinabove using the measurements obtained from the pulley-responsive potentiometer arrangement. The resultant signal produced is proportional to the nip force measured in p.l.i. (pounds per lineal inch) and is displayed at the operators bench.

This signal is also compared with a nip set point signal to produce an error signal used in controlling the counterbalancing pressure on the rider roll and hence the nip forces. An operational amplifier/servo driver combination acts as an integrator to ensure correction of steady state errors.

By connecting the nip set point controller through a variable resistance device back to a potentiometer which provides an output signal proportional to the changing diameter of the winding roll the nip can be programmed to vary linearly in accordance with the diameter of the winding roll at a slope or rate determined by the setting of the resistance device.

A switch is provided which disconnects the resultant nip signal line from the nip set point signal line so that the nip can be controlled manually in accordance with the reading of the nip indicating meter.

Other features and advantages of the invention will be set forth in or apparent from the detailed description of a preferred embodiment thereof found hereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic representation of a rider roll system incorporating the invention;

FIG. 2 is an explanatory diagram; and

FIG. 3 is a schematic circuit diagram of an electrical control system in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a winding assembly generally denoted includes first and second winder drums 112 and 114 which engage a roll 116 of a material such as paper wound on a central core shaft 118. Shaft 118 is supported in a vertically movable core shaft slide arm 120 and a hinged cover member 122 clamps over the shaft 118 to secure shaft 118 between cover member 122 and slide arm 120. Slide arm 120 moves up and down along a track 124 (a portion of which is shown in FIG. 1).

Winder drums 112 and 114 are individually spaced from a vertical line from the axis of core shaft 118 by a distance S as indicated, whereas the distance between the axis of shaft 118 and a line joining the axes of winders 112 and 114 is denoted II. It will be understood that as the roll 116 builds the distance H will increase.

In general, in order to measure the variation in distance H and in the diameter D of the roll 116, scaled down distances proportional to distances H and D are measured using the apparatus shown in the upper portion of FIG. 1. This apparatus includes a stainless steel cable 126 which is secured at one end thereof to core shaft slide 120 and is wound through a :1 ratio pulley system denoted 128 which includes first and second fixed pulleys 130 and 132 and first and second movable pulleys 134 and 136. Movable pulleys 134, 136 are mounted on a trolley or slide device 138 which rides on a linear track indicated at 140, the other end of cable 136 being affixed to trolley 138 as indicated. Trolley 138 includes flange bearings (not shown) which engage the hard steel rails of track 140 and first and second Negator springs 142 and 144 which serve both in forcing the trolley 138 against track 140 as well as in providing tension in the stainless steel cable 126 which tends to pull the trolley 138 upward. Negator springs 142 and 144 are respectively wound about mountings 142a and 144a on trolley 138 and are affixed at the free ends thereof to track 140. The natural bow of negator springs 142 and 144 forces the trolley rollers 146 and 148 to bear against the steel rail track 140.

A small sector of a pulley 150, mounted on and extending outwardly from trolley 138, is connected through first and second cables 151 and 153 to first and second pulleys 152 and 154, respectively, to provide measurements of distances H and D. Pulley 152 drives first, second and third potentiometers 156, 158 and 160 while pulley 154 drives a further potentiometer 162, rotation of the respective pulleys causing a corresponding variation in the setting of the associated potentiometers. Each of the potentiometers is a 50K., 0.2 percent linearity potentiometer, the pulley circumferences being designed such that the full movement of slide arm 120 will produce less than one full revolution of the potentiometer setting. The centerlines or axes of pulleys 152 and 154 are spaced horizontally by a distance S/5 as indicated, the factor 5, of course, being the reduction provided by pulley arrangement 130. It should be pointed out that other pulley ratios such as 6:1 and 7:1 may also be used. The vertical spacing of pulley 152 is H/S as shown whereas the vertical spacing between pulleys 152 and 154 is actually arbitrary in that more cable can be adjustably added as needed to provide the proper vertical separation. The radius of pulley sector 150 is equal to the respective radii of pulleys 152 and 154 so that by measuring the cable extension, that is, the change in the lengths of the cables 151 and 153 caused by movement of trolley 138 which is, of course, ultimately determined by the size of the roll 116, the distances between the center of pulley sector 150 and the centers of pulleys 152 and 154 are determined. Thus, the outputs of potentiometers 156, 158, 160 and 162 provide information as to the relative geometrical relationships between winder drums 112 and 114 and roll 116. These relationships are shown in FIG. 2, wherein, as indicated, potentiometers 156, 158, 160 provide an output proportional to the radius of roll 116 while potentiometer 162 provides an output proportional to -the distance l-I discussed hereinabove. The radii of winders 112 and 114 are, of course, fixed and are represented by r,, ohms as is discussed hereinbelow.

Referring again to FIG. 1, a rider roll 164 is positioned above and may rest upon roll 116 as described hereinabove. One possible counterbalancing system for counterbalancing the weight of rider roll 164 includes a fixed chain 166 which includes a loop portion 166a and which passes over a series of sprockets 168 and 170. A further sprocket 172 is positioned in the bight of loop 166a and is secured to the free end of the piston 174 of a pneumatic cylinder 176 which controls the force exerted by rider roll 164 on roll 116. The pressure in cylinder 176 is controlled through a control valve 178 which is, in turn, controlled by a servo control device 180. Pressure for the counterbalancing system is furnished by a supply source indicated at 182 and may be exhausted into a tank 184 depending on the position of control valve 178. A pressure operated potentiometer 186 serves in sensing the pressure supplied to cylinder 176. In practice, two cylinders, corresponding to cylinder 176, and the associated drive chains thereof are mounted on opposite ends of the rider roll 164, each supplying one-half of the total counterbalancing weight. However, because the cylinder sprocket 172 is positioned in the bight of chain loop 1660, each cylinder rod experiences full rider roll weight while providing only one-half of the normal stroke.

Pressure operated potentiometer 186 provides a direct reading of the lifting force exerted on rider roll 164. In practice, the rider roll 164 may be counterbalanced in the air in a floating or neutral position so that the rider roll 164 is balanced at a point just short of that where movement thereof takes place up or down. The corresponding pressure is the pressure necessary to counterbalance the weight of rider roll and knowing this pressure along with the dead weight of rider roll 164, which is a predetermined quantity, permits calibration of the system to be begun as will become more clear from the discussion hereinbelow.

Referring to FIG. 3, the output of potentiometer 156 referred to above is connected to the noninverting input of an operational amplifier 190. Amplifier 190 is connected as a very high impedance voltage follower so that the voltage pickup from potentiometer 156 is quite accurate even where very little current is drawn. The system power supply provides terminal voltages of plus 15 volts and minus 15 volts which are supplied to appropriate terminals of amplifier 190. Amplifier 190 is preferably a ceramic encapsulated l4-pin dual in-line package and the plus and minus supply voltages are connected to pins 11 and 6 respectively. These connections as well as others used in stabilizing the operation of amplifier 190, as well as the further operational amplifiers discussed hereinabove, have been omitted for purposes of clarity. Potentiometer 156 is connected to a positive l5-volt supply terminal 191.

The voltage output of amplifier 190, which of course is proportional to the diameter of roll 116, is connected through line 192 to a series of program cards 194 and 196 for use in related systems as well as to a digital voltmeter 198 which provides a direct reading of roll diameter. The output of amplifier 190 is also connected to the nongrounded end of potentiometer 158, the output of which is connected to the noninverting input of an amplifier 200. Amplifier 200 is also connected as a voltage follower and the output thereof is therefore proportional to the roll diameter squared. It will be understood that the terms diameter and radius are being used interchangeably here in that, of course, only differences in scale factors are involved. Although a monitoring output terminal 202 is provided for supervisory purposes, the chief use of the D output of amplifier 200 is in determining the weight in units such as pounds per lineal inch of the roll. A 10K., n-D /4 calibrate" potentiometer 204 is used to multiply the D output of amplifier 200 by the factor 1r/4 to produce an output corresponding to 1rD /4 which is, of course proportional to the area of the circular end of roll 164 or to the volume of a l-inch slice of roll 164. It will be appreciated that potentiometer 204 actually performs a division and thus in reality divides by l/1r divided by 4.

A further operational amplifier 206 is used to multiply the output of potentiometer 204 by the density of the paper in pounds per cubic inch to produce a measurement of the weight of a 1-inch slice of roll 164 in pounds per lineal inch. Operational amplifier 206 is connected to a summing amplifier so that the output voltage thereof is equal to minus the feedback resistance multiplied by the sum of all the voltages divided by the input resistances. The feedback resistance of amplifier 206 is formed by three thumbwheel adjustable resistance switches 208, 210 and 212 which permit the dialing in of a three digit number corresponding to the density of the roll material. For the specific system under consideration, the calibration factor is p.l.i. is equivalent to a minus lO-volt output from amplifier 206. The output of amplifier 206 is connected through a l0-K. resistor 214 to a summing point 216 which is, in turn connected to the inverting input of a further operational amplifier 218. Amplifier 218 is connected as a summing amplifier and a IO-K. feedback resistor 219 is connected in the feedback path thereof.

A pressure signal to be summed with the density signal produced at the output of operational amplifier 206 is produced by pressure operated potentiometer 186 which is connected to a minus -volt supply terminal 220. As set forth hereinabove, potentiometer 186 senses the cylinder pressure used in counterbalancing the weight of rider roll 164. The corresponding output signal produced thereby is connected to the noninverting input of a further operational amplifier 222 connected as a voltage follower. The output of amplifier 222 is thus proportional to pressure and is properly calibrated using a cylinder area calibrate potentiometer 224, potentiometer 224 being used to adjust the amount of current flowing to a further operational amplifier 226 when the rider roll 164 is free floating or counterbalanced. A positive current also flows into amplifier 226 as provided by a connection through a fixed l2-K. resistor 228 to a plus l5-volt supply terminal, the positive current thus being somewhat greater than 1 milliampere. This current is balanced by a negative current produced by cylinder area calibrate potentiometer 224 by appropriately varying the setting of potentiometer 224 when rider roll 164 is counterbalanced.

It will be appreciated that rider roll 164 cannot, of course, produce a lifting force so that a diode clamp 232 is connected in the feedback path of amplifier 226 to prevent amplifier 226 from producing apositive output. It is noted when the cylinder 176 is bottomed out" or when rider roll 164 reaches a mechanical stop (not shown) the pressure sensed by potentiometer 186 will rise to relatively very large values. However, as stated, amplifier 226 should only produce a negative output, the negative sign indicating a downward force, and hence the use of diode clamp 232. It should be pointed out that although only one diode is shown in FIG. 3 two diodes are actually used so that the DC voltage drop of forward conduction across one of the diodes is subtracted by matching this drop with an opposite reverse voltage drop across the other diode.

A weight calibrate potentiometer 234 is adjusted such that the output voltage of amplifier 226 is proportional to the weight of rider roll 164 with no counterbalancing provided, that is, with rider roll 164 permitted to freely drop downward with the maximum weight thereof. Considering a specific example, for a 100-inch machine a scale factor of 2000 pounds is used for a minus l0-volt output.

The output of amplifier 226 is fed through a 50-K. face potentiometer, 23.6, the setting of which is proportional to the web width and, the full SO-K. adjustment corresponding to a 100-inch face. Suitable; multipliers may be used for higher face widths. The output of potentiometer 236 is connected to summing; point 2'16.

The output; voltage of amplifier 218 is connected through a vector resolution network generally denoted 238 which includes potentiometer 162 connected in the input circuit of a further operational, amplifier 240 connected as a summing amlifier, and potentiometer- 160 connected in the feedback path of amplifier 240. Vector resolution network 238 is utilized to resol e. the total downward, force in the vertical direction, this weight being thesumofi the paper weight p.l.i. and the rider roll p.l.i. as discussedabove, into first and second vectors directly normallyto; the winder drums 112 and 114, respectively, at the point ofi'contact with paper roll 116. It will be appreciated that these vectors will represent the sought-after nip TGQ-S against: the winder. drums 112., 114. To determine these forces. the: total downward force ismultiplied by the cosine of the angle, 0.- (see FIG, 2); between the vertical force vector and h vectcr-ncrm l'to one ofthe winder drums 112', 114. It will appreciated that: the. normal force against each of the windlcr' 1.13 1115v 1112', 114. is. actually one-half of the total r sultant: orce, this. fact: being: taken, care of by a change of scale as.:exnlained hereinhelow. To perform the multiplication in question the input to vector resolution network 218, which is, of course, a signal proportional to the total downward force, is divided by the resistance setting of potentiometer 162 and multiplied by the total feedback resistance of amplifier 218 which is the sum of the resistance setting of potentiometer 160 and the resistance of a fixed resistor 242. This latter resistance, termed r above,is equal to the radius of winder drums 112, 114 and is obtained by multiplying the radius of drums 112, 114 by the amount of ohms change per inch of radius of the wound paper roll 116 produced by potentiometers 156, 158 and 160. The change in scale factor mentioned above means that the output of amplifier 240 is minus 10 volts equals 50 p.l.i. rather than plus 10 volts equals p.l.i. as in the input, the minus sign of course resulting from the sign inversion produced by amplifier 240. v I

A 0.0l-microfarad capacitor 244 is connected across the feedback resistances 160 and 242 of amplifier 240 to avoid oscillations caused by cable capacitances. h

The output of amplifier 240 is fed through a 100-K. resistor 243 to a 100-microampere, moving-coil, taut band meter'245 to provide a direct indication of the nip force in p.l.ilThu s, as discussed hereinabove, a direct indication of nip force has been obtained without the need forgoing underneath the machine with load cells, this latter approach havinga number of serious disadvantages because of the strain placed onan active indicator in this position. A

In order to maintain the nip force at a desired level, the actual nip force signal is compared with a set point signal corresponding to the desired nip force. In general, the nip forceis controlled by changing the pressure at counterbalancing cylinder 176 which changes the output of amplifier 222 and ultimately the rider roll signal summed together with the vertical force signal at summing point 216. Hence, a closed loop system is provided going through pressure sensing potentiometer 186 and returning through amplifier 240. Although a hydraulic system is being discussed here it will be appreciated that an electrical to pressure transducer could also be used in conjunction with a pneumatic servo system or a pneumatically adjusted air pressure system where a rider roll corresponding to rider roll 164 was to be counterbalanced by pneumatic cylinders.

Turning to a more specific consideration of the nip control system, a nip adjustment potentiometer 246 is connected to a plus 15-vo1t supply terminal 248 and the output thereof is connected to a summing point 250 through a 33-K. resistor 252. Potentiometer 246 is used by the operator to set the desired amount of nip and the control represents about 0 to 22 p.l.i. starting nip, the 22 p.l.i. corresponding to current fed through 33-K. resistor 250 with a l5-volt driving signal with l milliamp of current proportional to 50 pounds per lineal inch as a conversion factor. The output of amplifier 240 is connected through a 10-K. resistor 254 so that with a nip slope control potentiometer 256 described hereinbelow adjusted down to zero, the inputs at summing point 250 sum to zero when the actual nip and desired nip signals are equal.

When these signals are unequal, the resultant output at summing point 250 is fed to a further operational amplifier 258 connected as a summing amplifier. Amplifier 1.18 controls the operation of a servo driver 260 which is connected through a 27-ohm resistor 262 to the servo valve coil 264 of servo 180 of FIG. 1. Amplifier 258 is connected to servtdriver 260 through a l-K. resistor 266 and a 5-K. flow/gain potentiometer 268. Flow/gain potentiometer 268 can be used to clamp servo driver 260 to some proportion of the plus 12- volt and minus l2-volt range of the driver, for example, to a range between plus 4 and minus 4 volts. This will limit the amount by which the servo valve coil 264 can be driven and thus the degree of opening of the servo valve 178, by limiting the travel of the valve spool. Hence, the lowering of the rider roll 164 can be effected at a controlled rate.

The use of 27-ohm resistor 262 is required because of the nature of the particular servo driver 260 used, driver 260 requiring an output impedance of about 100 ohms. It should be noted that the servo driver 260 acts as an automatic fuse under circumstances such as where the control cable to the servo valve 178 is cut or pinched or the power supply is shorted.

Considering the operation of the nip control system and assuming that the starting nip is set to a nominal figure of 10 p.l.i., if the resulting nip is not high enough, the current flowing from summing point 250 to amplifier 258 tends to be positive and will, therefore, cause a negative voltage to be fed to servo driver 260. Servo driver 260 is connected as a one-toone or unity gain amplifier follower and thus will produce a minus voltage at servo coil 264 to cause a reducing or bleeding off of pressure in counterbalancing cylinder 176 and, consequently, a reduction in counterbalancing pressure and a corresponding increase in the pressure with which rider roll 164 bears against roll 116. The decrease in counterbalancing pressure will be sensed by pressure sensing potentiometer 186 and will be reflected at meter 245 an increase in nip force which is, of course, correct.

A feedback stabilization network for the nip control system includes a SO-K. feedback potentiometer 270 connected in series with a 33-K. resistor 272 and in parallel with a 0.22- microfarad capacitor 276 and a 47-K. resistor 274. A pair of l-microfarad capacitors 278 and 280 are connected in series with this resistor-capacitor combination as shown and thus the feedback stabilization network contains no direct feedback path, all feedback passing through at least one capacitor. Hence amplifier 258 and servo driver 260 act as an integrator having a very high gain and, consequently, if any steady state error exists the servo driver 260 will continue to gradually shift until the error is eventually overcome. The integrating action is produced through the use of two time constants determined by the feedback network, the current flow to amplifier 258 being stabilized so that servo valve 178 does not swing wildly between the open and closed portions thereof as the system attempts to compensate for variations.

The nip slope control potentiometer 256 mentioned hereinabove is connected through first and second diodes 282 and 284 to the output of amplifier 190 and through an l8-K. resistor 286 to summing point 250. Diodes 2 82 and 284 are used to drop the signal current to near zero when winding begins at the core. Hence, although no output is produced at this time, by adjusting the nip slope when rider roll 164 is in engagement with core shaft 118 any desired slope can be called for without adjusting the starting nip point. The desired additional positive current flowing through potentiometer 286, which rises linearly after diodes 282 and 284 begin to conduct, is added at summing point 250 in the same way as the nip set point current from potentiometer 246 is added and hence causes a gradually increasing nip force to be applied between the time at which winding begins and the lift off point of rider roll 164. The nip slope potentiometer 256 can be used to delay lift ofi by several inches if, for instance, the rider roll 164 tends to bounce, or to anticipate the eventual rise in nip force when rider roll 164 is lifted. This rise is caused by the fact that after rider roll 164 lifts the nip force against the winder drums 112, 114 has nowhere to go except to increase and as long as this is going to occur it is preferable to program the rise by permitting the nip force rise on a linear program. Further, it is noted where it is necessary to maintain rider roll 164 on roll 116 with a small amount of force, the output of amplifier 226 may be very near to or at zero volts. To combat this the cylinder area calibrate potentiometer 224 may be deliberately set incorrectly to ensure that an output is produced by amplifier 226. On the other hand, potentiometer 224 may be deliberately set in the opposite direction so that rider roll lift off can be achieved slightly prior to the time at which the weight of rider roll 164 becomes zero. This approach avoids teasing or hesitating in the lifting off of the rider roll 164.

A switch 290 is used to switch operation of the system from automatic to manual. With switch 290 in the manual position thereof the output of amplifier 226 is connected through a 33- K. resistor 292 to the input of amplifier 258. Under these circumstances, the only feedback available is that provided from the output of amplifier 226- which is negative and which depends strictly on the downward force of the rider roll 164. By balancing a current proportional to the rider roll force against the setting of nip adjustment potentiometer 246, the rider roll force can be regulated directly. The nip meter 245 will still indicate the proper nip existing against each winder drum 112, 114 at this time so that a program of nip versus diameter may be set up manually without resorting to the automatic control system. The manual regulation of the nip also provides an emergency backup control.

Although the invention has been described in detail with particular reference to a preferred embodiment thereof, it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

I claim:

1. A rider roll control system for controlling the nip forces on the winder drums of a winding assembly including a movable winding roll on which a web of material is to be wound and a rider roll for engaging the winding roll comprising counterbalancing means for counterbalancing the weight of the rider roll, control means for controlling said counterbalancing means responsive to the movement of the winding roll as the roll builds in size means for producing at least one electrical output signal proportional to a predetennined geometrical relationship related to the actual size of the winding roll and means responsive to said electrical output signal for providing a signal indicative of the actual nip forces on the winder rolls whereby said output-signal-responsive means is employed for controlling said counterbalancing control means.

2. A system as claimed in claim 1 wherein said outputsignal-responsive means includes means for producing a signal corresponding to the load exerted by the rider roll, electrical output-signal-responsive means for producing an output corresponding to the vertically downward force exerted by the winding roll and summing means for algebraically summing said rider roll load signal and said winding roll force signal.

3. A system as claimed in claim 2 wherein said rider-rollload-signal-producing means includes means responsive to the counterbalancing force exerted by said counterbalancing means for producing an output signal in accordance therewith.

4. A system as claimed in claim 3 wherein said rider-rollsignal-producing means includes means for producing a signal proportional to the dead weight of the rider roll and further summing means for summing said dead weight signal and said counterbalancing force signal.

5. A system as claimed in claim 4 wherein said counterbalancing force responsive means includes a pressure-sensitive potentiometer and a calibration potentiometer connected to the output of said pressure sensitive potentiometer for balancing out said dead weight signal when said rider roll is in a neutral, floating position.

6. A system as claimed in claim 5 further comprising further potentiometer means for dividing the output of the first-mentioned summing means by a factor proportional to the width of the web of material to produce a signal proportional to r der roll force per unit width of the web.

7. A system as claimed in claim 1 further comprising means for producing an output signal in accordance with a desired nip force, summing means for summing said desired nip force signal with said actual nip force signal and for producing an error signal in accordance with the algebraic sum of said signals.

8. A system as claimed in claim 7 further comprising means responsive to said error signal for controlling said counterbalancing control means.

9. A system as claimed in claim 8 wherein said error-signalresponsive means comprises integrating means, including an operational amplifier and a servo driver, for providing integration of the error signal.

10. A system as claimed in claim 9 wherein said operational amplifier and said servo driver share a common feedback path.

11. A system as claimed in claim 11 wherein said feedback path provides first and second time constants.

12. A system as claimed in claim 9 further comprising a potentiometer connected between the output of said operational amplifier and the input of said servo driver for controlling the output range of the servo driver. I

13. A system as claimed in claim 2 wherein said output signal responsive means includes control means for controlling the electrical output signal in accordance with the density of the material to be wound'on the winding drum.

14. A system as claimed in claim 13 wherein said control means includes an operational amplifier connected as. a summing amplifier and a variable resistance device connected in the feedback circuit of said amplifier. 7

15. A system as claimed in claim 14 wherein said variable resistance device comprises a plurality of thumbwheel-controlled resistance switches for providing'setting of the density directly in pounds per cubic inch.

16. A system as claimed in claim 1 wherein said winding roll movement responsive means comprises a movable slide device and a pulley arrangement for causing movement of said slide device a scaled down amount proportional to the'movement of said winding roll.

17. A system as claimed in claim 16 further comprising first and second fixed pulleys, means for connecting said fixed pulleys to said slide device, and potentiometer means for producing an output signal responsive to the length of the connection between said pulleys and said slide device'as reflected in the rotation of said pulleys.

18. A system as claimed in claim 17 wherein said slide device includes an outwardly extending portion in the shape of a pulley sector having a radius equal to the radii of the fixed pulleys the centers of said first and second pulleys are spaced apart by a scaled down distance proportional to the distance between the centers of the winder drums and a vertical line through the'central axis of the winding roll, the center of said first pulley is positioned beneath the center of said pulley sector by a scaled down distance proportional to the perpendicular distance between the central axis of the winding roll and a line joining the centers of said winder drums, and the second pulley is directly beneath said pulley sector.

19. A system as claimed in claim 18 wherein said potentiometer means comprises first, second and third potentiometers controlled by said first pulley for producing an electrical output proportional to the diameter of the winding roll and a fourth potentiometer controlled by said second pulley for producing an output proportional to the perpendicular distance between the central axis of the winding roll and a line joining the central axes of the winder drums.

20. A system as claimed in claim 16 wherein said slide means includes a linear track, a trolley member, means for mounting said trolley member for movement along said track including first and second coil springs mounted on said trolley and having the free ends thereof secured to said track.

21. A system as claimed in claim 18 wherein said pulley arrangement includes first and second fixed pulleys and first and second movable pulleys secured to said movable slide device.

22. A system as claimed in claim 20 wherein output-signalresponsive means comprises a first operational amplifier having an input connected to the output of said first potentiometer and an output connected to said second potentiometer, a second operational amplifier having an input connected to the output of said second potentiometer for producing an output proportional to the diameter squared of the winding roll, calibration potentiometer means for multiplying the output of said second potentiometer by a factor proportional to the constant 1r/4, a third operational amplifier having a variable feedback resistance calibrated in material density units of force per cubic unit for producing an actual winding roll weight output signal in units of force per lineal unit width.

23. A system as claimed in claim 22 further comprising means for producing a signal proportional to the effective weight of the rider roll in units of force per unit width, means for summing said effective rider roll weight signal and said actual winding roll weight signal to produce a resultant signal, and means for resolving said resultant signal to the nip components thereof including a further operational amplifier connected as a summing amplifier and having said fourth potentiometer connected in the input circuit thereof and a feedback resistance formed by said third potentiometer and a resistance proportional to the diameter of the winder drums connected in the feedback circuit thereof, said system further including an indicating meter connected to the output of said further operational amplifier. 1

24. A system as claimed in claim 22 further comprising a variable resistance device connected between the output of said first operational amplifier and said summing means.

.25. A system as claimed in claim 7 further including switching means for disconnecting said actual nip force signal from said summing means to provide manual control of said nip force.

26. A system as claimed in claim 7 further comprising means for producing a desired nip force signal proportional to the actual diameter of the winding roll and means for adding said actual diameter signal to said desired nip force signal. 

1. A rider roll control system for controlling the nip forces on the winder drums of a winding assembly including a movable winding roll on which a web of material is to be wound and a rider roll for engaging the winding roll comprising counterbalancing means for counterbalancing the weight of the rider roll, control means for controlling said counterbalancing means responsive to the movement of the winding roll as the roll builds in size means for producing at least one electrical output signal proportional to a predetermined geometrical relationship related to the actual size of the winding roll and means responsive to said electrical output signal for providing a signal indicative of the actual nip forces on the winder rolls whereby said output-signal-responsive means is employed for controlling said counterbalancing control means.
 2. A system as claimed in claim 1 wherein said output-signal-responsive means includes means for producing a signal corresponding to the load exerted by the rider roll, electrical output-signal-responsive means for producing an output corresponding to the vertically downward force exerted by the winding roll and summing means for algebraically summing said rider roll load signal and said winding roll force signal.
 3. A system as claimed in claim 2 wherein said rider-roll-load-signal-producing means includes means responsive to the counterbalancing force exerted by said counterbalancing means for producing an output signal in accordance therewith.
 4. A system as claimed in claim 3 wherein said rider-roll-signal-producing means includes means for producing a signal proportional to the dead weight of the rider roll and further summing means for summing said dead weight signal and said counterbalancing force signal.
 5. A system as claimed in claim 4 wherein said counterbalancing force responsive means includes a pressure-sensitive potentiometer and a calibration potentiometer connected to the output of said pressure sensitive potentiometer for balancing out said dead weight signal when said rider roll is in a neutral, floating position.
 6. A system as claimed in claim 5 further comprising further potentiometer means for dividing the output of the first-mentioned summing means by a factor proportional to the width of the web of material to produce a signal proportional to rider roll force per unit width of the web.
 7. A system as claimed in claim 1 further comprising means for producing an output signal in accordance with a desired nip force, summing means for summing said desired nip force signal with said actual nip force signal and for producing an error signal in accordance with the algebraic sum of said signals.
 8. A system as claimed in claim 7 further comprising means responsive to said error signal for controlling said counterbalancing control means.
 9. A system as claimed in claim 8 wherein said error-signal-responsive means comprises integrating means, including an operational amplifier and a servo driver, for providing integration of the error signal.
 10. A system as claimed in claim 9 wherein said operational amplifier and said servo driver share a common feedback path.
 11. A system as claimed in claim 11 wherein said feedback path provides first and second time constants.
 12. A system as claimed in claim 9 further comprising a potentiometer connected between the output of said operational amplifier and the input of said servo driver for controlling the output range of the servo driver.
 13. A system as claimed in claim 2 wherein said output signal responsive means includes control means for controlling the electrical output signal in accordance with the density of the material to be wound on the winding drum.
 14. A system as claimed in claim 13 whErein said control means includes an operational amplifier connected as a summing amplifier and a variable resistance device connected in the feedback circuit of said amplifier.
 15. A system as claimed in claim 14 wherein said variable resistance device comprises a plurality of thumbwheel-controlled resistance switches for providing setting of the density directly in pounds per cubic inch.
 16. A system as claimed in claim 1 wherein said winding roll movement responsive means comprises a movable slide device and a pulley arrangement for causing movement of said slide device a scaled down amount proportional to the movement of said winding roll.
 17. A system as claimed in claim 16 further comprising first and second fixed pulleys, means for connecting said fixed pulleys to said slide device, and potentiometer means for producing an output signal responsive to the length of the connection between said pulleys and said slide device as reflected in the rotation of said pulleys.
 18. A system as claimed in claim 17 wherein said slide device includes an outwardly extending portion in the shape of a pulley sector having a radius equal to the radii of the fixed pulleys the centers of said first and second pulleys are spaced apart by a scaled down distance proportional to the distance between the centers of the winder drums and a vertical line through the central axis of the winding roll, the center of said first pulley is positioned beneath the center of said pulley sector by a scaled down distance proportional to the perpendicular distance between the central axis of the winding roll and a line joining the centers of said winder drums, and the second pulley is directly beneath said pulley sector.
 19. A system as claimed in claim 18 wherein said potentiometer means comprises first, second and third potentiometers controlled by said first pulley for producing an electrical output proportional to the diameter of the winding roll and a fourth potentiometer controlled by said second pulley for producing an output proportional to the perpendicular distance between the central axis of the winding roll and a line joining the central axes of the winder drums.
 20. A system as claimed in claim 16 wherein said slide means includes a linear track, a trolley member, means for mounting said trolley member for movement along said track including first and second coil springs mounted on said trolley and having the free ends thereof secured to said track.
 21. A system as claimed in claim 18 wherein said pulley arrangement includes first and second fixed pulleys and first and second movable pulleys secured to said movable slide device.
 22. A system as claimed in claim 20 wherein output-signal-responsive means comprises a first operational amplifier having an input connected to the output of said first potentiometer and an output connected to said second potentiometer, a second operational amplifier having an input connected to the output of said second potentiometer for producing an output proportional to the diameter squared of the winding roll, calibration potentiometer means for multiplying the output of said second potentiometer by a factor proportional to the constant pi /4, a third operational amplifier having a variable feedback resistance calibrated in material density units of force per cubic unit for producing an actual winding roll weight output signal in units of force per lineal unit width.
 23. A system as claimed in claim 22 further comprising means for producing a signal proportional to the effective weight of the rider roll in units of force per unit width, means for summing said effective rider roll weight signal and said actual winding roll weight signal to produce a resultant signal, and means for resolving said resultant signal to the nip components thereof including a further operational amplifier connected as a summing amplifier and having said fourth potentiometer connected in the input circuit thereof and a feedback resistance formed by said third poteNtiometer and a resistance proportional to the diameter of the winder drums connected in the feedback circuit thereof, said system further including an indicating meter connected to the output of said further operational amplifier.
 24. A system as claimed in claim 22 further comprising a variable resistance device connected between the output of said first operational amplifier and said summing means.
 25. A system as claimed in claim 7 further including switching means for disconnecting said actual nip force signal from said summing means to provide manual control of said nip force.
 26. A system as claimed in claim 7 further comprising means for producing a desired nip force signal proportional to the actual diameter of the winding roll and means for adding said actual diameter signal to said desired nip force signal. 